The Good: 1) There's enough variety in gameplay that things do not drag on too much; 2) The art is great and the animation is fluid. Yeah so you re-use the character portrait, who cares; 3) Scarcity of water seems realistic, and I got enough from just traveling; 4) Combat is infrequent and relatively easy, given how easy ammo is to find; 5) Many of the medal scenes (e.g., 'badass') are pretty cool, and break up the tedium that can set in.
The Neutral: 1) Adjusting the random events based on how much time/miles have elapsed might also be a good idea. Sure, at first, there might be a lot of gangs and survivors. By mile 120 or after a month or two, however, very large hordes, people trying to cannibalize each other, and similar situations are bound to happen; 2) a few more zombie types to fight would be good.
The Bad: 1) I think your games in general would benefit from more story. Not a lot more story, but a good intro and ending would suffice; 2) During my play, every scripted scene had the same hard-coded outcome. These sorts of scenes are an opportunity to get inside the head of the character you are portraying. There could easily be a few dozen more, where a given choice randomly yields good or bad consequences. See the small generator grocery store many times get boring.